textproduct: Quad Cities

KEY MESSAGES

- Heat and humidity will build across the area Monday through Thursday this week. Heat indices of 95 to 100+ are expected, highest for areas south of I-80. A Heat Advisory has been issued for areas along and south of I-80 for Monday through Wednesday.

- How hot conditions get this week will depend on where any showers/storms develop.

- There is a near-daily risk of showers and storms possible more likely for areas along and north of I-80.

SHORT TERM /THROUGH MONDAY/

Issued at 219 PM CDT Sun Aug 30 2026

Scattered showers and isolated thunderstorms continue across much of the area this afternoon as a mid-level shortwave continues to sweep over the area on the northern side of a heat dome. This heat dome will support very warm and muggy conditions for much of the area this week (more on that in just a bit!). Strong to severe storms are not anticipated with this activity, given meager mid-level lapse rates and SBCAPE values of only 500 to 1000 J/kg per the SPC Mesoanalysis page. This will still be ample instability for some isolated storms this afternoon, most likely along and north of Highway 30.

Tonight will likely be nearly a carbon-copy of this morning's conditions, with additional chances (10-40%) of showers and storms developing as a nocturnal southwesterly 30 to 40 knot low-level jet (LLJ) builds, enhancing convergence along it. At this time, the more likely areas to see this activity continues to be over northwestern Illinois and adjacent areas of eastern Iowa, closer to the nose of the LLJ. Overnight lows are expected to dip to the lower 70s area- wide.

Heat and humidity are expected to increase further on Monday as the heat dome builds northward. The LREF ensemble cluster analysis remains in very good agreement on this occurring, with 500 mb heights of 594 decameters over the southern Plains/southern MS River Valley regions. High temperatures on Monday are expected to warm to the upper 80s over northwest Illinois/northeast Iowa to the lower/middle 90s over southeast Iowa/northeast Missouri/west-central Illinois. Heat indices are forecast to exceed 100 degrees for areas along and south of I-80, and indeed the 30.12z HREF exceedance probabilities of 100 degrees for heat indices are 60-90% over these areas. This has prompted the issuance of a Heat Advisory for these areas. There are some signals in the global models for a mid-level shortwave to sweep through the area Monday afternoon that could support another round of showers and storms, which could tamper down the heat farther north.

LONG TERM /MONDAY NIGHT THROUGH SUNDAY/

Issued at 219 PM CDT Sun Aug 30 2026

Monday night through Tuesday will need to be watched for the potential of isolated strong to severe storms over the northern portions of our region as additional shortwave impulses ride the top of the heat dome. This severe storms risk appears to be conditional, and thus, confidence is low for storms to become severe. However, given sufficient MUCAPE values around 2000-3000 J/kg, combined with 25 to 35 knots of 0-6 km shear, the convective parameter space would be supportive of strong/severe storms late Monday night and again Tuesday afternoon if anything develops. Overall, the large scale forcing from these shortwaves remains pretty weak, so SPC continues to have only a Marginal Risk (level 1 of 5) for severe storms for these time frames. The Tuesday afternoon storm potential will have the potential to limit daytime heating, and thus, limiting the heat indices. Storms will be most likely north of I-80 for each time frame.

Outside of the storm threat, we will continue to have hot and humid conditions over at least the southern portions of the area where storm chances are much more limited through much of the week. Confidence in the hot conditions Tuesday through Thursday remain high, given the latest ECMWF EFI/Shift of Tails values for high temperatures Tuesday through Thursday are in excess of 0.8 to 0.9 (even some values over 0.95 in isolated spots), along with Shift of Tails values around 1. This suggests high confidence in anomalously warm high temperatures, although not extreme values based on the lower Shift of Tails. With the potential for these anomalously hot conditions to last this week, we've decided to have the Heat Advisory go through the daylight hours Wednesday. It's entirely possible for the advisory to be extended into Thursday, given LREF ensemble exceedance probabilities of 100 degree heat indices approaching 50% across our southern two tiers of counties. Additionally, overnight lows might not dip below 75 degrees Monday night through Wednesday night, so this would compound the heat stress - even at night. There is potential for some record warm low temperatures during this period. See the Climate section below for the current records.

AVIATION /00Z TAFS THROUGH 00Z TUESDAY/

Issued at 552 PM CDT Sun Aug 30 2026

Scattered showers and isolated storms to push east into northern IL over the next hour. Some light returns may bring some sprinkles through 04z at DBQ, otherwise VFR conditions will prevail. A strengthening LLJ late tonight/early Monday to bring a risk of LLWS to the terminals once again until 14z. Some showers may develop near BRL around sunrise and have included PROB30 wording for this occurrence.

Another weak shortwave to round the top of the ridge Monday afternoon bringing scattered showers and isolated storms to areas across northern and northeast IA, similar to what occurred today. Some hi-res ensemble guidance would place some of this activity near DBQ and have added a PROB30 group for this potential. Winds to remain southerly through the period under 15kts.

CLIMATE

Issued at 222 PM CDT Sun Aug 30 2026

Record Warm Low Temperatures:

August 30: KMLI: 75/1947

August 31: KDBQ: 74/2000 KMLI: 75/2000

September 1: KDBQ: 73/1937 KMLI: 75/1913

September 2: KDBQ: 74/2011 KMLI: 77/1913

September 3: KDBQ: 73/1939 KMLI: 76/1939

September 4: KDBQ: 71/1912 KMLI: 74/2018

DVN WATCHES/WARNINGS/ADVISORIES

IA...Heat Advisory from 1 PM Monday to 7 PM CDT Wednesday for IAZ063>065-067-068-076>078-087>089-098-099. IL...Heat Advisory from 1 PM Monday to 7 PM CDT Wednesday for ILZ015-016-024>026-034-035. MO...Heat Advisory from 1 PM Monday to 7 PM CDT Wednesday for MOZ009-010.